Snap action switch



Nov. 18, 1958 J. HOLLIS ETAL 2,861,149

' SNAP ACTION SWITCH Filed Feb. 9, 1956 INVENTORS ARTHUR J. HOLL/S ROBERT E. SHAW United States Patent SNAP ACTION SWITCH Arthur J. Hollis, Danvers, and Robert E. Shaw, Beverly, Mass, assignors to Sylvania Electric Products Inc., Salem, Mass., a corporation of Massachusetts Application February 9, 1956, Serial No. 564,455

6 Claims. 01. 200-113 This invention relates generally to snap action electrical contact switches having repetitive, self-induced opening-and-closing cycles, and more particularly to such switches in which the opening and closing of contacts is effected by a resilient vane to which bending stresses are alternately applied and released.

Such switches are especially useful for flashing the directional signal lamps of automotive vehicles.

Problems are presented in the design and production of such switches to meet stringent standards imposed by various automotive manufacturers. Such standards, which vary from one manufacturer to the other, may apply to the frequency of the operating cycle and to the division of the cycle between the period during which the contacts are closed and the period during which the contacts are open. For example, one manufacturer may require a switch which operates at 60 to 70 cycles per minute and Whose contacts are closed 40% to 50% of the time. On the other hand, the standards of another manufacturer may necessitate an operating frequency of 80 to 90 cycles per minute and contacts which are closed 50% to 60% of the time. Since slight variations occur in the formation of successive component parts and in their assembly into switch units, it has been diflicult to produce switches whose performance would uniformly fall within established tolerances. In order to obtain facility and economy of manufacture, it is highly desirable to provide means for adjusting the operation of switches after assembly.

It is accordingly a general object of our invention to provide a switch structure which may be manufactured economically.

Another object is the provision of a switch in which the operating characteristics may be adjusted after assembly. V

- In addition, our invention is directed to providing more positive engagement of the contacts during the portion of the operating cycle in which they are required to be closed. High speed switch action in prior devices has been obtained by providing a slender vane and a heat expansible wire or ribbon upon which a movable contact can be mounted. The heating of the ribbon by the passage of electrical current therethrough, expands it and releases vane-bending stress which moves the movable contact into or out of engagement with a fixed contact. Because of the pliability of the components which determine contact engagement, the contacts often formed either a high resistance connection when closed or one which chattered or was prematurely interrupted.

It is therefore an additional object of our invention to provide positive, low resistance continuity of engagement between contacts for the portion of each cycle during which closure is required.

The foregoing and other objects are achieved in accordance with our invention by a switch structure in which opening and closing of contacts is effected by a snap action of a substantially flat vane of resilient material. The vane has a concave deformation in one of F 2,861,149 Patented Nov. 18, 1958 its faces, a convex deformation generally normal to the concave deformation in the same face and an opening at the intersection of the two deformations. A ribbon of heat-expansible electrically-conductive material is secured under tension to the vane in angular relation with the deformations thus stress-deforming the vane about the convex deformation. In the stress-deformed condition of the vane a movable contact mounted on the ribbon is in engagement with a fixed contact disposed on a suitable base. The ribbon is heated by the passage of an electric current therethrough and the vane thus permitted to snap back to a pre-set condition in which it is bent along the concave deformation. In the preset condition of the vane, the contacts are disengaged.

Since neither deformation is disposed in alignment with the ribbon, access may be had to each deformation in order to effect changes in the operating characteristics of the switch. The central opening facilitates adjustments and, by eliminating an area which would otherwise be overstressed, permits the vane to be flexed more easily in two directions.

In addition, an improvement in contact pressure is achieved by securing a stiffening member to a portion of the vane. Since such a switch generally incorporates an audible signal producing member, such stiffening may advantageously be provided without the introduction of added components by suitably forming the member and securing it to the vane.

The foregoing and other objects, advantages and novel features of our invention will be clarified from the following description of an illustrative embodiment thereof, taken in connection with the accompanying drawings in which:

Figure 1 is a plan view of a switchaccording to our invention;

Figure 2 is a view of the switch in front elevation showing the contacts closed;

Figure 3 is a view of the switch in front elevation showing the contacts open;

Figure 4 is a plan view of a vane which is a component part of the switch;

Figures 5 and 6 are views of the vane in front and end elevation respectively showing deformation thereof under vane bending stresses;

Figures 7 and 8 are views of the vane in front and end elevation respectively showing pre-set deformation therein;

Figure 9 is a schematic diagram showing a typical application of the switch to signal lamp energization.

Turning now to the drawings and more particularly to Figures l-3, we will now describe an illustrative switch in detail. A base 20, of dielectric material such as a thermosetting phenolic, has upstanding thereon a vane mounting stud 22 and a fixed contact 24. The stud 22 supports a resilient rectangular vane 26 and a laterally extending arm 28. A ribbon 30, of electrically conductive, heat expansible material, such as Nichrome, is tautly secured to diagonally opposite corners 32, 34 of the vane 26 and carries a movable contact 36. The fixed contact 24 is electrically connected to a terminal 38 depending from the base 20;and the movable contact 36 is in electrical communication with another terminal 40 through ribbon 30, vane 26 and stud 22.

The vane 20 has a central opening 42 and includes pre-set deformations along the longitudinal center-line 44-46 and along the transverse center line 48-50 as shown in Figure 4. The deformation along the line 4446 which is the vanes major deformation in its preset condition is a relatively shallow V, concave in the upper surface of the vane 26 as shown in Figure 8. The deformation along the line 4850 is convex in the upper face of the vane 20. As illustrated in Fig. 7, the pre-set condition of the vane 26 is relatively flat in a longitudinal direction.

As the vane 26 is mounted on the stud 22, it is in a stress-deformed condition illustrated in Figs. and 6 which are schematic in nature, the'ribbon 30 having been omitted for greater clarity. It will be understood, however, that the vane 26 is forcibly retained in its stressdeformed position by the contracted ribbon 30. At assembly, the vane 26 is deformed about its transverse center line 4850 and the ribbon 30 is secured to the corners 32, 34, as by spot welding, for example. The corners 32, 34 are priorly bent, downwardly, as shown in Figs. 58 to facilitate securing of the ribbon 30 thereto. The arm 28 is secured along the longitudinal edge of the vane 26 at several points between the intersection of the line lit-50 with the longitudinal edge and the corner 32. The vane 26 is thereafter fixed upon the stud 22 with the fixed contact 24 engaged by the movable contact 36 which is mounted on the ribbon 30. The depth of the V or deformation along the line 44-46 is substantially decreased in the stress-deformed position of the vane 26. On the other hand, the vane 26, whose deformation along the line 4850 is negligible in the pre-set condition illustrated in Fig. 7, is substantially deformed in this direction under the stress applied by the contracted ribbon 30 as shown in Figure 5.

The operation of the switch will now be more particularly described with reference to Figure 9 in which an illustrative circuit in shown and Figures 2 and 3 which sh w the contacts 2 36 engaged and disengaged respectively. A battery 52 has one terminal connected to the contact 36 through a control switch 54 and ribbon 30 represented schematically as a resistance. The other terminal of the battery 52 is connected to the fixed contact 24 through signal lamps 56. When the switch 54 is closed by the driver of the vehicle to signal a turn, the contacts are engaged as shown in Figure 2 and current flows from one. terminal of the battery 52 through the lamps 56. the fixed contact 24, the movable contact 36, the two h lves of the ribbon 30 in parallel, the vane 26 and the switch 54 to the other terminal of the battery. The lamps 56 are therefore initially energized. Current flowing through the ribbon 30 causes it to heat and expand. When the expansion of the ribbon 30 is sufficient, its tension is overcome by the energy stored in the vane 26 which returns with a snapping motion to its pre-set condition shown in Figures 7 and 8. This snap motion moves the corner 34 of the vane 26 upwardly, causing the vane to strike the free end of the arm 28 and producing an audible click which is repeated with each operation of the switch to inform the driver that his signal lamps are flashing. The motion of the vane 26 includes an upward motion of the free end thereof as a result of the flattening of the transverse deformation and an added upward motion of the corner 34 by the increased deformation about the line 44-46. The effect is to disengage suddenly the contact 36 at the cen tral portion of the ribbon 30, thereby de-energizing the lamps 56. Thereafter, the ribbon 30 cools and contracts until the stiffness of the vane 26 is overcome and the latter is returned to its stress-deformed condition, the contacts 24 and 36 re-engaging for the beginning of a new cycle.

In the circuit shown in Figure 9, it will be appreciated that the lamps 56 are the major resistive element which largely determine current flow, rate of heating of the ribbon 30, and hence the operating frequency of the switch. However, in a circuit of a given resistance the operating frequency of the switch may be increased by making the longitudinal deformation greater relative to the transverse deformation. Similarly, the period of time in each cycle during which the contacts 24, 36 are closed may be lengthened by increasing the transverse deformation. These modifications, which may be made with simple hand tools after the switch assembly has been tested, have the effect of broadening manufacturing tolerances and of correspondingly reducing rejections of completed assemblies. On the other hand, the mode of aflixing the arm 28 to the vane 26 results in more positive contact engagement without the necessity of added structural elements which would unduly complicate assembly and accordingly increase cost.

In addition, by decreasing the spacing between the free end of the arm 28 and the vane 26, the return of the vane to its pre-set condition may be limited to secure a corresponding increase in operating frequency.

What we claim is:

1. A snap action switch comprising: a base; a substantially flat vane of electrically conductive material having a central opening, a concave deformation in a face thereof extending from opposite edges of the vane to said opening, and a convex deformation in the same face extending along a line passing through said opening and disposed generally normal to the concave deformation; electrically conductive means for supporting said vane in spaced relation with said base; means in thermally-expansive relationship with the vane alternately to apply and release vane bending stresses along a line obliquely disposed relative to each of said deformations to effect snapping of the vane between a stress-deformed position in which the vane is bent along the line of said convex deformation and a pre-set restored position in which the vane is bent along said concave deformation; a movable contact mounted on said vane at a point having substantial motion, relative to said base, resulting from said snapping action; a stationary contact fixed to said base in the path of said movable contact for engagement with the latter in the stress-deformed position of the vane and separation therefrom in the restored position of the vane, said stationary contact and said previously-mentioned electrically-conductive means being spaced apart by said base but insulated from each other along a path through said base and a separate terminal on said base in electrical communication with each contact.

2. A snap action electric switch comprising: a dielectric base; a substantially flat rectangular vane of electrically conductive resilient material having a central opening, a longitudinal concave deformation in a face thereof extending from the ends of the vane to said opening and a transverse convex deformation in the same face extending from the sides of the vane to said opening; electrically conductive means adjacent a longitudinal edge of said vane at a point intermediate a corner and the intersection of the transverse deformation with said edge for supporting said vane in spaced relation with said base; means in thermally-expansive relationship with the vane alternately to apply and release vane bending stresses at diagonally opposite corners to effect snapping of the vane between a stressdeformed position in which the vane is bent along the transverse deformation and a pre-set restored position in which the vane is bent along the longitudinal deformation; a first contact mounted on said vane at a point having substantial motion, relative to said base, resulting from said snapping action; a second contact fixed to said base in the path of said first contact for engagement with the latter in the stressxleforrned position of the vane and separation therefrom in the restored position of the vane; and a separate terminal on said base in electrical communication with each contact.

3. A snap action switch comprising: a base; a substantially rectangular vane of electrically conductive material having a concave deformation extending between the ends thereof in a face of said vane along a longitudinal line, a convex deformation in the same face extending between the sides of the vane along a transverse line, and an opening at the intersection of the two said lines; an electrically conductive stud upstanding on said base and supporting said vane at a point spaced from said deformations and in spaced relation with said base; a heat expansible electrically conductive ribbon secured under tension to diagonally opposite corners of the vane whereby the latter is snapped between a stressdeforined position in which the vane is forcibly bent along the transverse deformation in the cold contracted condition of the ribbon and a preset restored position in which the vane is bent along the longitudinal deformation in the heat expanded condition of the ribbon; a movable contact mounted on said ribbon for motion therewith in response to the snapping motion of said vane; a stationary contact mounted on said base in the path of said movable contact for engagement with the latter in the stress-deformed position of the vane and separation therefrom in the restored position of the vane, said stationary contact and said previously-mentioned electrically conductive stud being spaced apart by said base but insulated from each other along a path through said base, and a separate terminal on said base in electrical communication with each contact.

4. A snap action switch comprising: a dielectric base; a substantially flat rectangular vane of electrically conductive resilient material having a central opening, a concave longitudinal deformation in a face thereof extending from the ends of the vane to said opening and a transverse convex deformation in the same face extending from the sides of the vane to said opening; an electrically conductive stud upstanding on said base and supporting said vane at a point spaced from said deformations and in spaced relation with said base; a heat expansible electrically conductive ribbon secured under tension to diagonally opposite corners of the vane whereby the latter is snapped between a stress-deformed position in which the vane is forcibly bent along the transverse deformation in the cold contracted condition of the ribbon and a pre-set restored position in which the vane is bent along the longitudinal deformation in the heat expanded condition of the ribbon; a movable contact mounted on said ribbon for motion therewith in response to the snapping motion of said vane; a stationary contact mounted on said base in the path of said movable contact for engagement with the latter in the stress-deformed position of the vane and separation therefrom in the restored position of the vane; and a separate terminal on said base in electrical communication with each contact.

5. A snap-action switch comprising: a dielectric base; a substantially flat rectangular vane of electrically conductive material having a central opening, a concave longitudinal deformation in a face thereof extending from the ends of the vane to said opening, and a transverse convex deformation in the same face extending from the sides to said opening; an electrically conductive stud upstanding on said base and supporting said vane at a point spaced from said deformations and in spaced relation with said base; a heat-expansible electrically conductive ribbon secured under tension to diagonally opposite corners of the vane whereby the latter is snapped between a stress-deformed position in which the vane is forcibly bent along the transverse deformation in the cold contracted condition of the ribbon and a pre-set restored position in which the vane is bent along the longitudinal deformation in the heat expanded condition of the ribbon; a movable contact mounted on said ribbon for motion therewith in response to the snapping motion of said vane; a stationary contact mounted on said base in the path of said movable contact for engagement with the latter in the stress-deformed position of the vane and separation therefrom in the restored position of the vane; a stiffener member applied to a portion of the vane; and a separate terminal on said base in electrical communication with each contact.

6. A snap-action switch comprising: a dielectric base; a substantially rectangular vane of electrically conductive material having a central opening, a concave longitudinal deformation in a face thereof, extending from the ends of the vane to said opening, and a transverse convex deformation in the same face extending from the sides to said opening; an electrically conductive stud upstanding on said base and supporting said vane at a point spaced from said deformations and in spaced relation with said base; a heat-expansible electrically conductive ribbon secured under tension to diagonally opposite corners of the vane whereby the latter is snapped between a stress-deformed position in which the vane is bent along the transverse deformation in the cold contracted condition of the ribbon and a pre-set restored position in which the vane is bent along the longitudinal deformation in the heat expanded condition of the ribbon; a movable contact mounted on said ribbon for motion therewith in response to the snapping motion of the vane; a stationary contact mounted on said base in the path of said movable contact for engagement with the latter in the stress-deformed position of the vane and separation therefrom in the restored position of the vane; an arm having a mounting portion secured to said vane about the mounting point of the latter, and a free end positioned in the path of a movable portion of said vane for engagement thereby with sound-producing impact; and terminals on said base each in electrical communication with one of said contacts.

References Cited in the file of this patent UNITED STATES PATENTS 2,041,775 Mottlau May 26, 1936 2,166,238 Davis July 18, 1939 2,266,537 Elmer Dec. 16, 1941 2,615,106 Schmidinger Oct. 21, 1952 2,756,304 Welsh July 24, 1956 

